This disclosure relates generally to optical communications, and in particular but not exclusively, relates to a dispersion compensator that can be used in an optical communications network.
Fiber-optic networks are increasingly being used in many industries, most notably telecommunications and computer networks. Transmission speeds and distances can at times, however, be limited based on various factors. One of these factors is chromatic dispersion, which occurs when a pulse of light traveling down an optical fiber broadens.
Such pulse broadening typically occurs as different wavelength components or colors within the pulse move at different speeds along the fiber, with the shorter wavelength components traveling faster than the longer wavelength components. Thus, a pulse may broaden and ultimately may overlap with another pulse, thereby distorting the data in a signal. This effect may become increasingly pronounced at high bit rates, as additional factors may contribute to chromatic dispersion (e.g., temperature, humidity, aging, and stress of the fiber).
In an effort to reduce chromatic dispersion and allow for longer transmission distances and greater throughput of data, several techniques are used. One technique is to use a dispersion compensating fiber (DCF) that can introduce negative dispersion over relatively short distances, thereby offsetting positive dispersion accumulated by the pulse traveling through the fiber. However, each portion of fiber generally requires a unique length of DCF in order to provide a correct amount of compensation. As such, DCFs are not readily tunable as changing properties of a DCF often requires changing the DCF itself, which is a process that can be time-consuming and inefficient.
Another technique includes the use of dispersion compensation gratings. One type of grating is a chirped in-fiber Bragg grating, which reflects each wavelength component at different points to compensate a dispersed pulse. Like DCFs, however, the amount of dispersion compensation provided cannot be adjusted easily. Moreover, the gratings may sometimes over-compensate or under-compensate at certain frequencies.
Accordingly, chromatic dispersion reduces the efficiency of fiber optic networks by limiting transmission distances and throughput of data. Known methods to solve this problem such as use of DCF and dispersion gratings, may have drawbacks, such as not being easily adjusted and/or not providing a suitable compensation amount.